1. Technical Field
The present invention relates to a technology of controlling a tension of a recording medium in an image forming apparatus which detachably holds the recording medium on which an image is formed on a rotational shaft by winding up the recording medium in a roll shape.
2. Related Art
A recording apparatus in JP-A-10-086472 records an image using a printing unit with respect to continuous paper which is supported by a transport drum which is arranged between two transport rollers, while transporting the continuous paper by rotating the two transport rollers which wind up the continuous paper. In addition, in an apparatus which performs image forming on a recording medium such as continuous paper, it is possible to transport the recording medium using a so-called roll to roll method. In the roll to roll method, rotational shafts are respectively provided at both ends of a transport path of the recording medium, and both ends of the recording medium are supported by the rotational shafts, respectively, by being wound in a roll shape. In addition, the recording medium is transported from a roll which is supported by one rotational shaft to a roll which is supported by the other rotational shaft. In addition, in general, the recording medium is detachably supported by the rotational shaft so as to be easily exchanged.
Meanwhile, it is preferable to stabilize a support of a recording medium using a support member by applying a large tension to the recording medium which is supported by the support member in order to perform good image forming with respect to the recording medium which is supported by the support member such as a transport drum. For this reason, the recording medium is stretched between two rollers which interpose the support member therebetween using a large tension. However, the large tension is not only generated by a torque of rollers which interpose the support member therebetween, and is also generated subsidiarily by a torque of rotational shafts which support both ends of the recording medium. Accordingly, when forming an image, such a large torque is not necessary in each of rollers interposing the support member therebetween.
On the other hand, when detaching the recording medium from the rotational shafts, since applying of the tension to the recording medium using a rotational shaft from which the recording medium is detached, the rotational shaft does not support a generation of the tension with respect to the recording medium which is supported by the support member any more. As a result, for example, there is a concern that a detaching work of the recording medium may not be smoothly performed, or the like, because the roller on a side of the rotational shaft of which support is lost, and from which the recording medium is detached cannot resist the tension which is originally applied to the recording medium on the support member, and the recording medium may deviate.